Dental implants have developed into a well established art. When an appropriate implant is properly installed, the patient can expect many years of comfortable and effective service.
There are two principal classes of dental implants. One is the subperiosteal implant which surmounts the bony structure with a post or posts rising from it to support a bridge or denture. The objective is for this implant to become attached to the bone by tissue ingrowth. It does not enter into the bone structure. This class of implant does have some successes, but its potential for success, and its applicability to many operative conditions are less than one would desire.
The other class of implant is the endosteal implant which is inserted into the bony structure. In some endosteal implants, blades or anchors are sometimes provided, especially when osseointegration is not expected to occur. This is the situation where the material of construction is such that it does not become osseointegrated.
It has been learned that osseointegration can and does occur when the implant is made of or surfaced with titanium and its alloys. It also occurs when the material is coated with hydroxylapetite (HA). However, unless the material is titanium, the risk exists that the HA may vanish, and that the implant will later be lost because the underlying material did not osseointegrate.
U.S. Pat. No. 5,004,422 issued to Robert H. Propper, the inventor describes implants that are made of titanium or that are coated with HA, and a method for implanting them. This patent is incorporated herein in its entirety for its showing of such implants and of suitable materials, properties, and installations for osseointegration. The disclosures in this patent are directly applicable to the instant invention.
Implants according to the Propper patent function well for many persons. For other persons, neither the Propper implant nor any other osseointegrated implant known to the present inventor will serve. For example, in many patients the mandibular nerve in the lower jaw is too close to the surface of the bone structure to permit an implant of suitable length (depth) to be implanted. This is because the operative recess is too shallow to receive a long enough implant to be successfully osseointegrated without contacting the mandibular nerve. Any contact with the mandibular nerve can lead to numbness or a burning sensation of the lip and chin, both potentially permanent. Many patients are experiencing this numbness because of nerve injury caused by the repositioning procedure necessary for the implantation to be made.
In the upper jaw, the maxillary sinus is the problem. The sinus is best not entered, and taking an impression of a socket that is in communication with the sinus in the upper jaw is to be discouraged. The upper jaw of many patients does not provide enough bone sufficiently remote from the sinus to allow the use of an implant whose shape relates to that of a tooth with a single root, or with multiple roots.
It is an object of this invention to provide an osseointegratable implant with supplementary stabilizer means which themselves will osseointegrate. Then the main portion of the implant-conforming to an operative recess of relatively shallow depth can be quite short, and can be implanted in such very shallow recesses with no risk to the mandibular nerve or to the maxillary sinus, while still making an acceptable implant. Of course it is necessary to provide an implant which can be fitted into the operative recess. This is nor necessarily as simple as it sounds. For a single-root tooth, the socket from which it was extracted is often used for the recess. However, multiply-rooted molars whose roots diverge present an entirely different problem. Even such a tooth which was extracted could not usually be reinserted into the socket from which it was extracted because of geometrical interferences. There is a septum between the root recesses, and the recesses are not axially aligned. It is an object of this invention to provide an operative recess which can receive an implant suitable to replace much of the function of a multiply-rooted tooth.
There is another problem with osseointegrated implants which this invention intends to overcome. It is the possibility of bacterial entry into the recess which will lead to implant failure, and excessive height of the post, which enables the tongue and mastication to work at the implant and tends to loosen it. This invention attends to these problems.
Also, especially for single-crown implants, the abutments provide an important anti-rotation function.